A former Swiss private banker says he plans to hand over data on hundreds of offshore bank account holders to the WikiLeaks website at a London news conference on Monday.

Rudolf Elmer once headed the office of Julius Baer in the Cayman Islands until he was fired by the bank in 2002. He is scheduled to go on trial in Switzerland on Wednesday for breaching bank secrecy.

He and Jack Blum, a former U.S. Congressional investigator and Washington lawyer who represents whistleblowers, are scheduled to appear at a news conference in London on Monday morning, where they are planning to hand over to WikiLeaks two compact discs which allegedly will contain names and account information of around 2000 individuals who have parked money offshore.

Organisers of the event say they believe WikiLeaks founder Julian Assange has agreed to appear at the event to personally receive the information.

However, the presence of Assange at the event is not certain, due to a court order largely restricting his movements to a mansion in eastern England, where he is residing while British courts consider a request from Swedish authorities that he be extradited to Sweden to face questioning about allegations of sexual misconduct.

On Sunday, Elmer told Reuters that he hoped his appearance at the news conference would both call attention to offshore financial abuses and promote WikiLeaks as a mechanism for other whistleblowers to air their stories.

The main thing is educating society about offshore abuses and how they work, he said.

I believe in the system of WikiLeaks, Elmer continued. Such a thing has to exist. WikiLeaks was my last hope. I couldn't get my message out. WikiLeaks may be the only means to get my message out to society. I would like to help get WikiLeaks back on track again.

Blum, Elmer's lawyer, told Reuters: The story is really about banks and banking, about bank secrecy and the damage it does to society when it's employed to hide tax evasion, money laundering and corruption.

Neither Elmer nor his lawyer are expected to release any specific information about the identities of the individuals named in the material Elmer plans to hand over to Assange.

Some, if not most, of the material has already been handed over to government authorities in countries where the account holders are believed to reside.

Elmer told the Swiss newspaper Der Sonntag that the data involved multimillionaires, international companies and hedge funds from countries including the United States, Germany and Britain.

He said the data came from at least three financial institutions, including Julius Baer, covered the period from 1990 to 2009, and included documents leaked to him from other whistleblowers.

Sources close to the whistleblower said he fears that any release of names could compromise official investigations which might be under way into the contents of the material.

In addition to information from Baer bank, the data Elmer is planning to hand to WikiLeaks may also relate to financial dealings at two other banks, one of them South African, the sources said.

The sources said Elmer has some expectation that WikiLeaks will vet and even investigate the material before making it public on the internet.

WikiLeaks itself is not known to have any capability for conducting investigations, however, and has worked through partners in the media to vet previous material -- such as its most recent gradual release of a cache of classified U.S. State Department cables -- before making it public.

Elmer is facing trial in Zurich for allegedly violating tough Swiss bank secrecy rules.

He and his lawyer maintain that the case is unfair because the material that he allegedly leaked -- including some material on alleged offshore tax evasion abuses already published by WikiLeaks -- originated in the Cayman Islands, where Swiss authorities arguably lack jurisdiction.

Elmer also maintains that the allegations against him relate to him allegedly violating bank secrecy rules by making financial records available to Switzerland's own tax authorities.

(Additional reporting by Emma Thomasson in Zurich; Editing by Jason Neely)

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